1. Field of the Invention
The present invention relates to a rock drill bit for rotary crushing machining of rock, which comprises at least one leg carrying a journal provided with bearing races in order to cooperate via a bearing element with bearing races in a rotatable roller provided with crushing means. The leg is made from a parent material with substantially homogenous hardness and comprises a leg tail provided to resist entrance of drill cuttings into the bearings. The invention further relates to a method for hardening a rock drill bit.
2. Description of Related Art
It is previously known to protect a roller drill bit leg end from wear by providing it with protective inserts and/or hard facing. The hard facing is necessary especially at the leg tail, where there is not enough space to mount the protective inserts. If the leg tail wears away, drill cuttings will quickly enter into the bearing races, which leads to bearing breakage or blocking of the bearings. The legs of a roller drill bit are carburized and hardened in order to achieve sufficient case depth and hardness of about 60 HRC on the bearing races. The core hardness on the other hand, lies about 30 HRC, in order to maintain suitable toughness and to decrease the risk for cracks and breakage. The low hardness of the legs however, wears the steel away too fast, unless protective inserts and hard facing are used.